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Details of Grant 

EPSRC Reference: EP/J501694/1
Title: Innovative fat reduction in chilled products using fresh mayonnaise
Principal Investigator: Murray, Professor B
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department: School of Food Science and Nutrition
Organisation: University of Leeds
Scheme: Technology Programme
Starts: 23 April 2012 Ends: 22 October 2013 Value (£): 100,263
EPSRC Research Topic Classifications:
Analytical Science Food processing
EPSRC Industrial Sector Classifications:
Manufacturing Food and Drink
Related Grants:
Panel History:  
Summary on Grant Application Form
Bakkavor have developed a new low fat mayonnaise (LFM) that shows great promise in providing similar mouth feel to

traditional (higher fat) mayonnaise. However, on contact with certain vegetable ingredients - namely onions, garlic, chives

or cabbage - the LFM starts to go extremely thick and viscous, giving the whole product the appearance of a gel which

precludes the use of this mayonnaise in many dips, dressings, dressed salads and other applications such as sandwich

fillings that also include these ingredients. This phenomenon has not been documented previously, so its origin is a

mystery at present.

Mayonnaise is a concentrated emulsion of oil droplets in a watery phase containing egg yolk and various other minor

ingredients, although the new LFM also contains added polysaccharide thickeners. As such, the instability is almost

certainly related to strong aggregation of the oil droplets and/or other ingredients within the formulation. Aggregation could

occur via: (a) the vegetable ingredients adding components to the aqueous phase that significantly decrease the repulsive

forces between the droplets or (b) the ingredients adding some extra cross-linking agent that strongly and irreversibly pulls

the droplets together. The principal aim is therefore to establish whether mechanisms (a) and/or (b) are operating in order

to suggest a viable commercial solution to this problem.

Mechanism (a) will be revealed through observations of the microscopic structure of the system and measurements on the

aggregation tendency of the droplets under controlled conditions. The change in the full apparent droplet size distribution

will be evaluated using various light scattering techniques in our laboratory. The surface charge properties of the the

droplets in selected systems will also be measured. Changes in the droplet size when samples are subjected to dilution

with simply water or detergents will be used. This can distinguish between very strongly aggregated droplets, which

appear still as large particles on dilution, versus weakly aggregated droplets that separate simply on dilution with water. A

possible mechanism of the gelation via (a) is the high ratio of polysaccharide thickeners to droplets, resulting in so-called

depletion flocculation (aggregation) of the system, but this should be entirely reversible on dilution. Droplet 'charge' (zeta

potential) measurements will provide evidence of any significant change in the surface structure or composition of the

stabilizing layer on the droplets that could help to explain their dramatic change in stability.

Mechanism (b) may be biochemical, since onions, garlic and chives are all produce enzyme (alliinase) activity on

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cutting/crushing that can produce free sulphydryl compounds that could cross-link the protein present (protein in the

aqueous phase or adsorbed to the droplet surfaces) and produce the gelation observed. Cabbage and other Brassica spp.

produce reactive isothiocyanates, nitriles, thiocyanates and also other sulphur species via the action of myrosinase

enzymes, so there is again the capability for protein cross-linking. Cross-linking reactions with the cellulose,

hemicelluloses and pectin components of the polysaccharide thickeners have not been documented, but the

polysaccharide may aid the formation of strong gels as they become incorporated into a cross-linking protein network.

The above measurements will therefore be performed on formulations where potential cross-linking agents are present or

absent. For example: whole onion puree, filtrate from filtered onion puree, enzyme-inactivated filtrate. Enzymes will be

deactivated by various heat treatments and or addition of cross-linking
Key Findings
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Organisation Website: http://www.leeds.ac.uk